1. Field of the Invention
The present invention relates to flying form table trusses for supporting cast in place concrete used, for example, for multiple slab areas, wide bays and multilevel building construction, and the invention further relates to screw jack legs for use in such trusses.
2. Description of Related Art
Flying shoring forms, which are used extensively for the above-mentioned purposes, are commonly referred to as flying form tables and are formed of a pair of parallel trusses, with bracing between the trusses, and with screw jack legs for supporting the trusses.
In use, a deck is supported on the tops of the trusses and is used to support concrete during the casting of a concrete slab. After the concrete has hardened, the flying form tables are lowered from the hardened concrete, and are then rolled outwardly from beneath the hardened concrete slab, so that they can be subsequently lifted by a crane, as if they were flying, and transported to the next slab casting area.
In conventional flying form tables, the trusses are constructed as elements of a fixed size, weight and construction, and are generally of a modular nature, which in practice predetermines the length of the tables in increments of approximately six feet to ten feet. The trusses of these conventional flying form tables are provided with support legs, in the form of screw jacks, which have predetermined, fixed locations on the bottoms of the trusses, irrespective of the shape of the concrete floor or other support upon which they bear during the casting operation.
In order to improve the adaptability of such an conventional flying form table trusses, the present inventor has developed an improved truss structure, which is disclosed in U.S. Pat. No. 4,831,797, issued May 23, 1989 to the present inventor, the disclosure of which is incorporated herein by reference.
The truss structure disclosed in the above-mentioned prior patent is formed of upper and lower chords, which are connected by rigid web members in the form of A frames, which are adjustable in position along the top and bottom chords. The contractor using the truss is, therefore, able to increase or decrease the spaces between the A-frames, depending on the thickness of the concrete slab to be cast, and can vary the lengths of his tables in increments of one foot.
The trusses employing these adjustable A-frames can therefore be assembled so as to match the requirements of individual projects, so that the user is provided with a flying form table which is tailor-made for his individual projects, and which avoids unnecessary materials and overhead costs.